Photocapacitance spectroscopy study of deep-level defects in freestanding n-GaN substrates using transparent conductive polymer Schottky contacts

We have investigated electronic deep levels in freestanding n-GaN substrates grown by hydride vapor phase epitaxy (HVPE) by means of a steady-state photocapacitance spectroscopy technique using transparent conductive polyaniline Schottky contacts. Two specific deep levels located at ∼1.7 and ∼3.1 eV below the conduction band were revealed to be significantly reduced compared to those in n-GaN layers grown by metal-organic chemical vapor deposition. This difference between them is probably due to extremely low concentrations of threading dislocations and residual C impurities in the HVPE-grown n-GaN substrates.